This is a large species of salamander, reaching a total length of 240 mm or more. It has established populations of both metamorphosing individuals (which develop from an aquatic juvenile form with larval characteristics to a terrestrial physical form with adult features) and neotenic individuals (which retain their aquatic larval characters throughout their life). Drainage of marshes has destroyed almost the entire Lake Lerma ecosystem with the consequence that the Lake Lerma salamander may have become locally extinct in that area. Conservation and restoration of this salamander’s habitat is an urgent priority in order to save this species from extinction in the wild.

Urgent Conservation Actions

Complete survey work to determine the current population status of the salamander; restore areas of suitable habitat.

The Lake Lerma salamander was first described by herpetologist Edward Harrison Taylor from an original specimen found east of Toluca in 1940. Despite not being seen in recent years, there is still hope of rediscovering this species in other areas of the Toluca Valley.

The family Ambystomatidae is also referred to as the mole salamanders because many live in burrows for much for their lives. They are found only in North America (from Canada down to Mexico), the majority (as is sometimes the case with the Lake Lerma salamander) metamorphose from aquatic larvae to become terrestrial adults that are rarely seen except in the breeding season, when they migrate to ponds to mate and deposit eggs.

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Evolutionary Distinctiveness

Order: Caudata

Family: Ambystomatidae

The family Ambystomatidae or “the mole salamanders” is included within the four earliest or most primitive family lineages of the order “Caudata” (the salamanders), diverging from all other salamanders in the Early Cretaceous period over 140 million years ago, around five million years before the koala and dolphin lineages diverged from their common ancestor. The small number of species that represent the genus Ambystomaare highly evolutionarily distinct members of both the salamanders and the amphibians as a whole.

The Lake Lerma salamander is capable of reaching sexual maturity in its neotenous form, retaining its aquatic larval characteristics such as fins and gills throughout its life. However, it is also able to metamorphose into the adult form and live a terrestrial life. Although this species has been little-studied, there are a couple of theories that may explain why some populations of the Lake Lerma salamander do not metamorphose. One idea is that the production or effectiveness of the hormone thyroxine is compromised, either by the species living in water bodies containing insufficient iodine (which is required in the manufacture of thyroxine by the body) or in water temperatures that are too cold for the thyroxine to be effective. This impacts upon the development of the species and sexually mature adults never develop adult characteristics but remain in the larval form. A second theory suggests that species evolving in pools surrounded by hostile terrestrial environments develop aquatic lives to obviate the need to exit the relative safety of their watery home. This is a common trait in species that inhabit high-elevation ponds. Since the Lake Lerma salamander inhabits various different water bodies across its range, and is able to disperse between them in its metamorphosed form, it is possible that the conditions in some of these water bodies are not conducive to metamorphosis.

Description

An Ambystomatid or mole salamander known only from the central highlands of the State of Mexico, near the city of Toluca, in the Río Lerma, Lake Lerma, and around Almolya, at an elevation of 2,800–3,000m above sea level. Mole salamanders are medium to large, stocky salamanders, measuring between 90 to 350mm from the tip of the nose to the end of the tail, which salamanders retain throughout their life. Males are often larger than females, partly due to their longer tails. Ambystomatids generally exhibit both aquatic “neotenic” larval (or aquatic and permanently juvenile in form with external, feathery gills) and terrestrial “metamorphosed” (or ground-dwelling, fully developed adult in form with reduced gills) stages in their wild populations. Ambystomatids are often boldly patterned as adults, with well-developed costal grooves (successive vertical grooves along the sides of the body), especially the metamorphosing varieties. They have a rather flattened body with a wide, flattened head, a large mouth and smooth skin with many glands. The tail is roundish or laterally compressed. During the breeding season males have a very swollen cloacal zone (the region around the reproductory and excretory opening in amphibians located underneath the base of the tail).

The Lake Lerma salamander has established populations of both metamorphosing individuals (which develop from an aquatic juvenile form with larval characteristics to a terrestrial physical form with adult features) and neotenic individuals (which retain their aquatic larval characters throughout their life). This is a large species of salamander, reaching a total length of 240 mm or more, about 115 mm of this measurement being accounted for by the tail. The skin is generally smooth, although it may appear slightly granular especially on the sides of the body. Eleven distinct costal grooves in the skin are visible along either side of the body. Where present, the dorsal fin (running from the back onwards) is low, rising to its maximum height along the tail. The toes are flattened, pointed and slightly webbed. The colouration of the skin in metamorphosed adults is uniform grey-black, with the tips of the digits being grey-cream. A closer inspection of the skin reveals that it is peppered with minute cream dots. In the larval form (or neotenes) this species is a deep purplish-black.

Ecology

The Lake Lerma salamander is a variable species, with individuals capable of reaching sexual maturity either in the metamorphosed (fully developed terrestrial adult) or neotenic (aquatic adult with larval characteristics) stage. In the neotenic form, individuals are capable of breeding despite the fact that they develop no other adult characteristics. This would be akin to a tadpole being able to breed without ever turning into a frog. Both population types breed in streams, lakes and moderately deep water reservoirs within their habitat.

Once the eggs are laid in water they are left to develop with no further participation by either parent. This species does not exhibit parental care.

Habitat

Its habitat is the Río Lerma and Lake Lerma in the Toluca Valley in the central highland of Mexico at an altitude of 2,800-3,000m above sea level. Metamorphosed individuals spend most of their time on land in grassland habitat. Neotenic populations and breeding individuals are found in streams, lakes and moderately deep-water reservoirs.

Distribution

Recorded only in the central highlands of the State of Mexico, near the city of Toluca, in the Río Lerma and Lake Lerma, and around Almolya, at 2,800–3,000m above sea level. It is possible that the species is more widespread in this general region, but more work is needed to investigate this prediction.

An extremely rare species of mole salamander. It has not been seen in recent years, likely to have suffered a local extinction in Lake Lerma itself due to drainage of the marshes and extreme levels of pollution in this water body. However, there is still hope of rediscovering the species in other areas of the Toluca Valley.

Population Trend

No population data is currently available for the species, although the population trend is assumed to be in decline in the IUCN Red List of Threatened Species.

Status

Listed as Critically Endangered on the IUCN Red List of Threatened Species because its extent of occurrence is less than 100km sq. and its area of occupancy is less than 10km sq., all individuals are in a single location, and there is a continuing decline in the extent and quality of its habitat, and in the number of mature individuals, around the city of Toluca.

Appendix II of CITES (the Convention on International Trade in Endangered Species of Wild Fauna and Flora), restricting its international trade to protect this species from over-harvesting in the wild.

Threats

Drainage of the marshes has destroyed almost the entire Lake Lerma ecosystem with the consequence that the Lake Lerma salamander may have become locally extinct in that area. The building of dams along the Lerma River in the Almoloya region in association with the villages of Tenango, Santa Maria, Jajalpa and San Pedro has destroyed essential habitat for this species, and there is generally a significant threat of habitat loss due to urban expansion. This has led to a castastrophic decline of the populations of the Lake Lerma salamander. The extremely high degree of pollution of the rivers and pools where this species breeds has also hastened its decline. In addition, animals have been captured as food for domestic consumption, while introduced predatory fish might also be a threat.

Conservation Underway

The Lake Lerma salamander does not occur in any protected areas, so the conservation and restoration of its remaining habitat is an urgent priority in order to prevent its extinction in the wild. However, this species is protected under the category Pr (Special Protection) by the Government of Mexico and received further protection from over-exploitation and harvesting from the wild by being placed on Appendix II of CITES (the Convention on International Trade in Endangered Species of Wild Fauna and Flora), which restricts its international trade.

The Lerma Axolotl inhabits a wetland that is been degraded. However, because of the importance of A. lermaense in the wetlands, as prey item and as a predator, and because it can survive in water and on land, this species can work as an umbrella species because byconserving this salamander and its habitat we can also protect other endangered species.Nevertheless, currently there is little information on the ecology and genetics of A. lermaense, which is necessary if we want to develop a conservation plan. Thus we aim to generate the information needed to underpin, foster and conduct a conservation strategy for A. lermaense.

Conservation Proposed

Further survey work is urgently required to determine the current population status of the species in the wild. Conservation and restoration of the Lake Lerma salamander’s habitat is an urgent priority in order to save this species from extinction in the wild. In addition to conserving wild habitat for this species, the IUCN Technical Guidelines for the Management of Ex situ Populations, part of the IUCN Red List of Threatened Species, recommend that all Critically Endangered species should have an ex situ population managed to guard against the extinction of the species. An ex situ population is ideally a breeding colony of a species maintained outside its natural habitat, giving rise to individuals from that species that are sheltered from problems associated with their situation in the wild. This can be located within the species’ range or in a foreign country that has the facilities to support a captive breeding programme for that species. It is not known whether it is possible to breed this species in captivity so further investigation is required into the possibilities of establishing an ex situ breeding programme for the Lake Lerma salamander.

However, any ex situ conservation measure is rendered ineffective if there remains insufficient natural habitat in which to release captive bred populations in the future. Clearly protected areas, sensitive land use techniques, habitat restoration and the control of introduced predatory fish populations are of paramount importance in rescuing this Critically Endangered mole salamander from extinction in the wild. Forest and stream restoration, and the protection of key sites in the Río Lerma, Lake Lerma, and around Almolya are therefore the primary actions required for the preservation of this species. Working with local communities on initiatives concerning habitat conservation and the reduction of fishing of Critically Endangered species like the Lake Lerma salamander would also be highly beneficial to environmental management in this area.

Although I cannot find any definitive information about what this species eats, I suspect it is similar to the other salamanders in the family Ambystomatidae which eat zooplankton when they are very small, and invertebrates such as worms, snails and insects when larger. They may also eat small vertebrates such as the larvae of other amphibians or small fish.

However, the most limiting factor for this species is likely to be the size of its mouth - it will probably eat most things close by that will fit!